[delinka]

Providing a protocol with a default concrete implementation of the interface? That's not passing code review here.

Would I have caught the bug? Probably not. But it looks like bad form to me to provide that default implementation to Greeter, so please rewrite your code.

[sharp11]

I’m curious to know why... Looks like typical mixin pattern, no?

[delinka]

An interface declaration is not the right place for implementation. If you want a default implementation, use a base class and inherit, overriding if you don't want the default.

This bug is now another good reason not to use default implementations on interfaces.

[jolux]

Protocol extensions are extremely powerful and safe if used correctly and not mixed with class inheritance as in this example.

[sharp11]

Ok, thanks. Sounds like you are not a fan of mixins! :)